High strength light-weight fiber ash composite material, method of manufacture thereof, and prefabricated structural building members using the same

ABSTRACT

A prefabricated structural building panel is disclosed. The panel includes a first sheet having inner and outer planar surfaces. A plurality of structural ribs are disposed on the inner surface of the first sheet and are interconnected to form a geometric design having a plurality of chambers. The first sheet and the structural ribs are integrally formed as a single unit from a fiber and fly ash composite material. In preferred form, the cement composite includes a mixture of a commercial grade fly ash having a high lime content and a dry flue-gas desulfurized fly ash.

RELATED APPLICATIONS

[0001] This is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 09/552,849, filed Apr. 20, 2000, the contents ofwhich are specifically incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to the field ofprefabricated building or construction materials and, more particularly,to prefabricated wall, roof, floor and decking panels. Specifically, thepresent invention relates to prefabricated building panels that arelightweight and environmentally friendly by utilizing recycled wastematerials to produce a green, low-cost family of products with superiorstrength characteristics and the composite material therefor.

[0004] 2. Description of the Prior Art

[0005] The present invention pertains to the production of structuralinsulated panels (SIP) in a highly advantageous and inexpensive mannerand pertains in particular to the use of fiber and fly ash cementcomposites to produce such panels. More than 50 million tons of fly ashare produced in the United States as a result of the electrical energygeneration process. Utilities generally dump the waste material intoponds to hydrate over a period of months and years. Althoughapproximately 25 percent of this material is used, the rest remainswaste material at this time. The present technology enables this wastematerial to be utilized as a main component in a hydraulic cementcapable of high strength and performance. Examples of such cementiousproducts are illustrated in U.S. Pat. Nos. 5,714,002, No. 5,714,003 andNo. 5,352,288.

[0006] There is a tremendous problem in the world today of having todeal with the disposition of waste material. Landfills are becomingfilled, and the burden on prime natural resources is increasing. Byrecycling waste materials, the pressure on landfills, air pollution andthe like are reduced. At the same time, trees are saved, and wastematerials, such as used carpeting and fly ash, may be reclaimed and putto use.

[0007] Many different techniques are used in the building industry forconstruction. In the United States, perhaps the most common is the frameor stick building. However, there are numerous other techniques andmaterials, such as various types of concrete block with variousinsulation performance, poured-in-place construction, panelizedconstruction, tilt-up panels, poured-in-place concrete panels, and brickstructures. Examples of such systems include those disclosed in U.S.Pat. No. 5,581,969 and No. 5,729,936.

[0008] Block construction falls into two classes: mortar-based systemsand mortar-less. Various block systems are available with manyincorporating special insulation systems to improve thermal performanceof a building. Most of these known block systems may also be constructedwith reinforced steel in order to improve wind and earthquakeperformance as well as general building strength and durability. Most ofthese systems require both interior and exterior finishing, althoughthere are numerous techniques where interior and exterior finishes suchas painting can be applied with a minimum cost. Many block systemsrequire internal plaster surfacing or the addition of drywall to theinside surface. Exterior siding or other finishing, such as stucco, isoptional and will depend upon design requirements. In general, this typeof construction yields a cost-efficient system that is often as good asa frame building, is more durable, has a higher appeal to qualitybuyers, is well understood by the building industry, and has good fire,moisture, rot, insect, wind, and earthquake performance. On the otherhand, while insulation is generally minimally sufficient to meet code,it is not exceeded by much of a margin. In addition, construction timeis about the same as or more than that for a frame building.

[0009] Frame buildings are generally low cost, relatively fast toconstruct, and widely used. There are many variations on frame building,but in general, it has limited fire and moisture performance, is subjectto rot and insect attack, has modest energy efficiency, requires bothinternal and external treatment once the frame has been constructed, andhas limited performance in high wind and earthquakes unless specialprecautions are taken.

[0010] Poured-in-place concrete systems, particularly the more modernstay-in-place form systems, have good durability, good fire and moistureperformance and are resistant to insects. With suitable reinforcing,these systems have reasonable performance in high-wind and earthquakeregions. However, they generally require interior and exterior treatmentafter the structure has been erected, and insulation value is limited.

[0011] Panelized systems, particularly SIPs, have limited fireperformance unless they are concrete based. Panelized concrete systemshave similar performance and characteristics to block systems. The newpanelized SIPs, consisting of a sandwich of two layers of orientedstrandboard (OSB) with a layer of expanded polystyrene (EPS), seek toprovide higher thermal performance than other building systems. However,they are less water and moisture resistant and can be subject to rot andinsect attack. They also still require finishing, both on the interiorand exterior of the structure. Their performance in high wind andearthquake conditions varies upon design but is generally considered tobe good.

[0012] Consequently, there is still a need in the construction industryfor a prefabricated wall, roof, floor and decking panel constructionthat meets all of the aforementioned objectives yet is lightweight, easyand inexpensive to produce, and takes advantage of environmentallyexpendable and recyclable materials rather than using limited naturalresources.

SUMMARY OF THE INVENTION

[0013] Accordingly, it is one object of the present invention to providea prefabricated structural building panel that has good durability, goodfire and moisture performance, is resistant to insects and hasreasonable performance in high-wind and earthquake regions.

[0014] It is another object of the present invention to provide highthermal insulation so that panels formed particularly for exterior wallsand roofs exhibit good energy efficiency.

[0015] It is another object of the present invention to provide aprefabricated structural building panel that is environmentally friendlyin that it utilizes fly ash and other materials that are environmentallydisposable.

[0016] Yet another object of the present invention is to provide aprefabricated building unit that is capable of being manufactured in acontinuous process so that it may be made in one large integral wallsection.

[0017] Still another object of the present invention is to provide aprefabricated structural building panel that is stronger than concrete,has all of the construction advantages of concrete, yet is less than 25%of the weight thereof.

[0018] To achieve the foregoing and other objects and in accordance withthe purpose of the present invention, as embodied and broadly describedherein, a prefabricated structural building panel is disclosed. Thepanel includes a first sheet having inner and outer planar surfaces. Aplurality of structural ribs are disposed on the inner surface of thefirst sheet and are interconnected to form a geometric design having aplurality of chambers. The first sheet and the structural ribs areintegrally formed as a single unit from a fiber and fly ash compositematerial. In preferred form, the cement composite includes a mixture ofa commercial grade fly ash having a high lime content and a dry flue-gasdesulfurized fly ash.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings which are incorporated in and form apart of the specification illustrate preferred embodiments of thepresent invention and, together with a description, serve to explain theprinciples of the invention. In the drawings:

[0020]FIG. 1 is a front perspective view, with portions cut away, of oneembodiment of a prefabricated panel constructed in accordance with thepresent invention;

[0021]FIG. 2 is a side perspective view, with portions cut away, ofanother embodiment of a prefabricated panel constructed in accordancewith the present invention;

[0022]FIG. 3 is a front perspective view, with portions cut away, of yetanother embodiment of a prefabricated panel constructed in accordancewith the present invention;

[0023]FIG. 4 is a schematic illustrating one process which may beutilized in the panel manufacture of the present invention;

[0024]FIG. 5 is a top perspective view of a panel formed from theprocess of FIG. 4 and illustrating a honeycomb geometric structuretherein;

[0025]FIG. 6 is a view similar to that of FIG. 5 but illustrating ageometric pattern of a series of offset rectangular boxes;

[0026]FIG. 7 is a view similar to that of FIG. 6 but illustrating ageometric pattern of a series of offset square boxes;

[0027]FIG. 8 is a view similar to that of FIG. 5 but illustrating ageometric pattern of a series of square boxes with no offset;

[0028]FIG. 9 is a front perspective view, with parts broken away, of anextruded structural building panel and/or siding and cladding panelconstructed in accordance with the present invention and includingsubstantially parallel interior channels;

[0029]FIG. 10 is a view substantially similar to that of FIG. 9 butillustrating the interior channels in the form of triangularcross-section;

[0030]FIG. 11 is a perspective view illustrating a panel constructed inaccordance with the present invention in the form of a strip of buildingsiding;

[0031]FIG. 12 is a perspective view of a wall panel section constructedin accordance with the present invention;

[0032]FIG. 13 is a perspective view similar to that of FIG. 12 butillustrating a one joining system incorporated into the edges thereoffor connecting adjacent wall panels;

[0033]FIG. 14 is a perspective view similar to that of FIG. 13 butillustrating one dovetailed joint section and web joining the adjacentpanels;

[0034]FIG. 15 is a perspective view similar to that of FIG. 14 butillustrating the joining of adjacent panels at right angles asrepresented by a corner web piece;

[0035]FIG. 16 is a cross-sectional view of a decking panel constructedin accordance with the present invention; and

[0036]FIG. 17 is a cross-sectional view of yet another decking panelembodiment constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The cellular panel construction of the present invention is acombination of three technologies. It is a panel which utilizes a newprocess and material that can produce virtually all the components usedfor the fabric of a commercial or residential building, such as floors,walls, roof and roof tiles, doors, trim, decking and the like. This newproduct and process uses a preferably rapid-setting fiber cementcomposite in a process that forms a lightweight grooved, honeycomb orbox structure that can be made in thicknesses varying from 8 mm({fraction (5/16)} inch) to 150 mm (6 inches) or more. The honeycomb orother geometric shaped cells or chambers may be filled with aninsulator, insulating foam, and/or aerated fly-ash cement, or simplyleft empty.

[0038] An example of this construction is illustrated in FIGS. 1-3.Referring to the FIGS. 1-3, a prefabricated structural building panel 10includes a first sheet or planar element 12 and a second similar sheet14. The panel 10 also includes a plurality of structural ribs 16disposed on the inner surface 18 of the first sheet 12. The ribs 16 arepreferably arranged in a geometric design to form a plurality ofchambers 20. In one preferred form, the geometric design is a honeycombstructure as illustrated in FIGS. 1-3. A second plurality of structuralribs 22 are also provided and extend from the inner surface 24 of thesecond sheet 14. The second ribs likewise form a geometric shape ordesign which creates a plurality of chambers 26. In preferred form, thefirst sheet 12 and the first ribs 16 are all formed as an integral unit,while the second sheet and ribs 14, 22 likewise are formed as anintegral unit. In the embodiment illustrated in FIG. 1, the sheets 12,14 are arranged facing each other so that the chambers 20 coincide withthe chambers 26 to form enclosed enlarged chambers when the sheets 12,14 are brought together.

[0039] In FIGS. 2 and 3, the honeycomb ribs 16, 22 are spaced from eachother so as to form a central space 28 between the ribs 16, 22. Thespace 28 may remain empty or, as in the illustrated embodiments of FIGS.2-3, an insulation material 30 may be positioned therein. In theillustrated embodiment, the insulation 30 also fills the pockets 20 and26 along with the space 28. The insulation 30 may be any desired type ofinsulating material but is preferably selected from an insulating foamsuch as polyisocyanurate, polyurethane, polyicynene or aerated fiber flyash. The insulation material selections are discussed in greater detailbelow.

[0040] The structural components of the panels of the invention are madefrom a fiber and fly ash composite. In preferred form, the compositematerial includes a mixture of fly ash, fly ash cement and fiber. Incertain instances, fine aggregates can be added to the compositemixture. More preferably, the composite includes 24-99% fly-ash and flyash cement mixture, 0-20% fine aggregate, and 1-12% fiber. The fiber maybe cellulosic or other materials, new or reclaimed, such as wood,carbon, metal, glass, and petrochemical or agricultural product fiber.Examples include corrugated cardboard and liner board, steel,polypropylene, a variety of agricultural fibers including kenaf, riceand wheat straw, and oil palm fronds, ash, black spruce, southernjuniper, cedar, and other wood fiber.

[0041] The cement may be a preferably rapid-setting Portland cement, orpreferably a cement based on fly ash, a waste product of the energygeneration utilities. It may also be made from slag, rice-hull ash, aswell as a host of other ashes. Two preferred embodiments of the cementare fly-ash cement based upon Powder River Basin (PRB) coal ash and flyash from the SYNAG process developed at Western Research Institute,Laramie, Wyoming. A particularly preferred material is disclosed in theaformentioned patent references. The composite of the present inventionis a unique material in that it draws upon three establishedtechnologies, implementing each and the combination of all of them in anew way, to produce a highly flexible, wide range of products that canbe produced under an automated manufacturing system.

[0042] The third component of the present invention panel is insulationin the preferred form of aerated fly ash. Several companies such asWehrhahn and Hebel in Germany have developed autoclave-based processesfor cellular concrete, as this type of material is known. In thisapplication we refer to aerated fly ash cement (AFA) or aerated fiberfly ash cement (AFFA). One company in Australia, Pan Pacific Engineering(PPE), has several licensees already established in the U.S. PPE doesnot require expensive autoclaving as part of its process. They are ableto produce AFA weighing one-fifth the regular weight of solid concrete.Although the panels of the present invention can be filled with otherinsulation materials, AFA/AFFA is an ideal filler and also has somelimited insulation value. In addition to PPE's process there are severalother similar processes for aerating cement, including those developedby Cementitious Foam Insulation, Weedsport, N.Y. and Cellular Concrete,LLC, Roselle Park, N.J. The panels of the present invention are filledto a depth of typically between one-half and one inch with AFA or AFFA,depending on economics and required performance. AFA/AFFA provides ameans of fixing screws and nails to the panels. Front and back panelsmay be cemented together and/or fixed together with an insulating layerof typically polyisocyanurate or polyurethane for greater strength andperformance. In the alternative, they can be extruded to simultaneouslyproduce a single integral unit. The panels of the invention can comefinished with a texture, e.g., stucco, on the exterior face, primed andready for painting. It requires no further cladding, making for a veryhigh value panel at modest cost. The interior face is finished in asimilar manner.

[0043] A wide variety of products can be formed using the presentinvention. In addition to the previously mentioned wall, roof and floormembers, thin-section products such as doors, roof-tile panels, and trimcan be made with the same process. These panels are made in complexforms. The same type of process is used for construction panels. Becausethese ribs can be formed using very high strength materials, most of thecomponent can be air, or filled with aerated cement or anotherinsulator. This provides for very lightweight construction of verystrong components. In addition, because the components are lightweight,they can be more easily and economically handled and installed on site.Transport costs are lower, too.

[0044] The same comments apply to a construction panel, which couldeasily measure in its finished form, 20 ft.×8 ft.×6 in. thick. Such apanel made in a solid material would weigh well over 7 tons. A panelmade using the construction of the present invention has a weight ofless than a quarter of this figure.

[0045] The fibers utilized in the present invention can be cellulose orother sorts, such as various plastics, fiberglass and the like. The flyash can be of various grades, such as Powder River Basin (PRB), class-Cfly ash, but also, using a different process, of other types andcombinations as described in greater detail below. In the case ofcellulose fiber, the present technology has the advantage of beingcapable of using fiber from renewable resources, such as agriculturalcrops like kenaf and other crops, as well as from the smaller limbs oftrees that are not otherwise utilizable for lumber. Where plasticfibers, such as polypropylene, are used, it is possible to use waste orrecycled fiber from the carpet industry. As fiber color is of noimportance for the manufacture of the present invention, this isadvantageous in that it utilizes fiber that would otherwise be wastedor, at best, underutilized.

[0046] The invention can work with wastepaper and cardboard of allsorts, both cellulosic and non-cellulosic fibers. Several preferredsolutions are possible, depending upon the kind of ash used in themanufacture of the composite. In the preferred embodiment of thisinvention, a coarse polypropylene fiber such as that used in carpetingface yarn is used. These fibers must be clean and cut to length. Variouscellulosic fibers may also be used, but these fibers must be prepared toinsure compatibility with the cement being used.

[0047] The structural grids in these composite materials are producedfrom fiber fly-ash cement mixtures, in the preferred embodiments of thisinvention. These grids are held in place in a monolithic, one-piecepanel by a foam binder, which also acts as insulation. The use of thefly-ash cement composite enables rapid setting of the grid and is anenvironmentally friendly material. Fly-ash cement does not emit anysignificant amount of greenhouse gas into the atmosphere. Portlandcement, on the other hand, emits one ton of CO₂ into the atmosphere forevery ton of cement made. Therefore, there is a significant advantage tousing the fly-ash cement as used in the composite of this invention

[0048] The closest common art prior to the present invention is the SIPpanel. These panels use flat sheets of OSB and an insulating sandwich toprovide the structure. They do not include the finishing material, whichis generally drywall on the interior surface and some form of siding onthe exterior surface. The OSB boards are generally glued or attached aspart of a spraying process in the case of polyurethane orpolyisocyanurate. These two latter forms of insulation expand to producean insulating sandwich between the two OSB boards. The present inventionis substantially different from and a substantial improvement over thatprior art, in that the two main component boards, interior and exterior,are manufactured with an integral grid pattern. This pattern providesconsiderable structural strength to the composite panel, even though thewalls of the grid are relatively thin, typically 3-10 millimeters inthickness. Another feature of the present invention is that a layer oflightweight, aerated, fiber fly-ash composite or other cement is placedin the bottom of each chamber. Our composite panel enables a builder tofix nails and screws into the fiber fly-ash composite layers, the outerskin of the grid, and the aerated fly-ash composite layer in the bottomof the chamber just under the outer skin. In many ways it behaves likewood, and very little cracking results when a screw is driven into it.This invention provides a step forward in the art in that very complexstructures can be produced. In the prior art, such complex, thin-walledstructures have not been possible, resulting in much higher weight andconsiderably lower strength-to-weight ratio.

[0049] The present invention is also to be distinguished from variousother kinds of SIPs. An important characteristic of the invention is theuse of a belt-press molding process or an extrusion technique, whichenable the material to be produced on a continuous basis. Anotherimportant characteristic of the material is that the insulation betweenthe two structural components of the composite panel can be formed withcavities or chambers. These allow services, such as plumbing andelectrical as well as HVAC, to be run through structures like floors orwalls. In addition, an exterior cavity may be formed to allow for aprimary and secondary moisture barrier. In the case of an exterior wall,a complex structure can be formed as a complete, integral wall unitincluding the exterior cavity. This is not found in any other SIP orconstruction panel that is manufactured as opposed to fabricated.Another feature of fly-ash cement is that it is resistant to sulfurattack. In addition, other features of the panel are that it isresistant to fire, moisture, rot, insects, high wind, and earthquakes.It has high-energy efficiency and may be rapidly constructed on site.

[0050] Referring now to FIG. 4, several forms of this invention producematerial continuously. This is a substantial improvement over of all ofthe prior art processes that are of a batch nature. The panels of thepresent invention are created by one of three primary processtechniques, all of which produce panels of any desired size on acontinuous basis. The building panel forming process of the invention isreasonably complex and state-of-the-art. Under computer control,material will be delivered to the mixing system in either process in theappropriate quantity and rate. To achieve both a uniform and continuousmaterial, the fiber and fly ash composite is processed in ahigh-intensity mixing system.

[0051] Three preferred processes for forming the panel of the inventionare possible including compression molding, specifically illustrated inFIG. 4, extrusion die molding and injection molding. The illustratedprocess of FIG. 4 first conveys the material to an infinite-end,compression forming machine. This is similar to the two illustratedconveyer belts traveling parallel to one another. The material will beon the bottom system or belt, while the top system or belt contains thegeometric pattern to be impressed into it. During the molding process,the material is held in compression until an initial set is reached andthen released as the upper mold rotates away.

[0052] Another related belt method is best described as a single-useincorporated-mold system. In operation, a pattern of spheroids 40 ofexpanding foam are extruded directly onto an endless, moving, steelsheet 42 from an above array of nozzles 44. The spheroids 40 adhere tothe steel sheet 42, forming the geometric pattern of the mold. The fibercement 46 is then applied over the spheroids 40, filling the voidsbetween. A surface skin with a thickness from 0 to 75 mm can also beapplied in this same process if desired. The rapid setting cement setsaround the spheroids, locking them into position. As the steel belt 42reaches its return roller 48, the formed sheet 50 containing the foamspheroids encapsulated by fiber cement would be directed onto anotherconveyance system 52, lifting it off the steel sheet used in the formingprocess.

[0053] Referring further to FIG. 4, an expanding insulating volume ofmaterial, typically but not necessarily, shaped as a sphere is depositedonto belt 42 via nozzle 44. These volumes of material form a mold whichalso acts as insulation in the final panel. The mold deposit rapidlyexpands to fill a spherical or other volume, while it is being drawnalong the belt. Some distance down belt 42, a composite 46 of fly-ashcement mixed with fiber 46 is fed onto the belt via a fiber-cementdischarge header. The fiber fly-ash cement mix is deposited on theinsulating volumes of material, typically made from polyisocyanurate orpolyurethane foam. The mix then travels under the second belt 54 whichcompresses the cement-laden belt 42. The length of belt 54 is chosen soas to allow sufficient time for the panel to be formed by the cement,and for the cement mix to set. At the end of belt 54 and belt 42, aseparation blade 55 immediately above belt one cuts away the moldedmaterial which adheres to the steel, or other, belt. A similarseparation blade 56 ensures that no cement tracks around the guide drumholding belt 54. The formed, and still setting, panel 50 then moves ontobelt 52 to complete the setting process.

[0054] FIGS. 5-8 illustrate four different geometric patterns that arereadily formed as a part of the panel 10. FIG. 5 illustrates thehoneycomb ribs 16 previously illustrated in FIGS. 1-3. FIG. 6illustrates a series of rectangular boxes 57 pressed out on a movingbelt press, while FIG. 7 illustrates a similar series of boxes 58 butwith square cross section. FIG. 8 illustrates a series of boxes 59 withno offset between consecutive lines of the 3-D structure. All of thesestructures of FIGS. 5-8 may be readily formed with a belt press systemillustrated in FIG. 4. The different configurations of the cells inFIGS. 5-8 provide for different strengths in orthogonal directions,depending upon the requirements of the application to which theresulting panel is to be applied.

[0055] For each of these forms the product could be made complete withthe backing sheet already formed to the box-shaped dividers, or thebacking sheet could be added later, with the boxes or other structuresopen. Once the open structure is formed, a top sheet can be applied, orthe spaces formed by the structure may be filled with an insulatingmaterial or low-density aerated fly-ash cement as discussed above.

[0056] In another preferred process embodiment of the invention, FIGS.9-13 illustrate product examples formed by combining extrusionprocessing technology with a rapid setting fiber fly-ash cementcomposite. Conceptually, one could think of this production methodologyas being the construction industry equivalent of profile extrusion ofplastics and composites. One important aspect of extrusion die moldingof the composition of the invention includes heating of the extrusiondie, electrically or preferably using hot water, to shorten the settingtime of the extruded composite structure. In this manner, the compositeis heated upon exiting the die thereby accelerating the setting processof the composite structure once formed even beyond its normally quicksetting time.

[0057] The illustrations of FIGS. 9-13 show a three-dimensional view ofa strip of building wall or panel 31 (FIG. 9) or siding 32 (FIG. 11).These are simply two examples of the many applications of the invention.The exterior surface of panel 31 or siding 32 can be textured foraesthetic appeal as part of the extrusion process or by means ofrollers, brushes and other similar means applied to the surface of theweb emerging from the heated extruder or from the belt press of FIG. 4.The ribs 33 of the panel 31 are preferably elongated in form to create aplurality of parallel chambers or channels 38 therebetween in lieu ofthe pockets or chambers 20, 26 of the prior embodiments.

[0058] The panel of FIG. 11 illustrates a flange 34 incorporated alongthe edge of the siding 32 to allow for fixing of the siding panel to thebuilding. The voids 38 extruded into the material between the ribs 33 ineither FIG. 9 or 11 may be left empty or may be filled with aninsulating foam such as polyisocyanurate, polyurethane, aerated fly-ashcement or another insulator or filler. The lower part of the drawing ofFIG. 11 shows an indent 35 in the bottom of the lowest void 38′ and howthat fits on to the piece of siding situated immediately below it,locking the sections into place. Other products having similar featurescould be made using the invention. In a practical sense this would havebeen very difficult to manufacture in accordance with known prior arttechniques because the drying time or setting time for Portland cementis several hours, and this would result in considerable sagging in theproduction of material containing voids such as the cross sectionsillustrated therein. By combining the use of rapid-setting fly-ashcement with an extrusion process, it is possible to produce crosssections such as that illustrated by the building siding in FIG. 11.

[0059] Another example of an extrusion using a rapid setting fiber basedfly-ash cement is shown in FIG. 10. The panel 36 shows an overall oblongcross section panel or member with reinforcing sections or ribs 37 setat opposing angles along the internal length of the formed section. Thisresults in a very high strength panel. The void 39 between the sectionsor ribs 37 may either be filled with an insulating or other foam or leftempty. FIG. 9 shows another example of an extruded oblong panel sectionwith adjacent closed channels 38 running the length of the panel.

[0060] By combining both panels 31 and 36 illustrated in FIGS. 9 and 10,and filling the space between such panels with, typically, severalinches of insulating foam such as polyisocyanurate or polyurethane, awall section or complete insulating panel 60 may be formed. FIG. 12shows a wall panel 60 cross section where both attributes of the paneldescribed in FIGS. 9 and 10 are embodied in a single panel. FIG. 12shows a whole wall section 60 including the exterior wall section 64 andthe interior wall section 62, with the edges joined by a web 66 creatinga central void space 67. Webs 66 could be included in intermediatesections joining the interior and exterior panels. In practice, anexterior wall section 64 might comprise an external extruded section ofapproximately 1 inch thickness, followed by three to five inches ofinsulating foam such as polyisocyanurate or polyurethane in the space67, followed by a 1 inch interior wall section 62. In this way an entirewall section could be extruded simultaneously.

[0061]FIG. 13 shows a wall panel 60 embodying the features illustratedin FIG. 12 but with the addition of a panel joining or connection systemon the edges of the panel 60. The case illustrated in this FIG. 13 showsdovetail joint sections 70, 72 at the web edges 74, 78, respectively.FIG. 14 shows one example of a further extrusion of fiber fly-ash cementin an edge matching dovetailed joint section, designed to hold twopanels 60, 80 together. The piece 82 may be separated along thecenterline 84, forming two pieces 86, 88 that are bolted together atregular intervals 90, typically every 12 to 48 inches of length. Thiseases assembly of the entire structure. In addition, cement and/orsealant can be added along the length of the joining piece 82 to ensurea solid, sealed joint for the panels.

[0062]FIG. 15 illustrates a structural beam member 92 that may be usedto join two panels 60, 80 at a corner. The corner joining piece 92 isextruded from fiber fly-ash cement composite and is designed to matchthe panel sections that it joins. The example shown in this FIG. 15 issimply one of many such corner joining systems that could be designedusing the principles of the present invention. Again, such sections areimpractical when made from Portland cement because of the extendedsetting time. When fiber fly-ash cement is used in the composite, thesetting times are fast enough that no significant sagging occurs as longas the mix is dry enough. In this case the panels 60, 80 may be recessedat their edges so that a flange 94 on the edge of the corner-joiningmember 92 can fit precisely to the recess (not illustrated) on the edgeof the wall. In the case of an exterior panel, this will help to ensurethat no moisture penetration takes place. It would also be possible todesign trim such that it overlapped the wall joint and stood out from itas illustrated in FIG. 15. Many such variations are possible and arewithin the scope of the present invention.

[0063]FIG. 16 illustrates a decking panel 95 particularly useful inoutdoor patios or decks. In this embodiment, the decking panel 95includes an upper panel portion 96 and a lower panel portion 97.Longitudinal ribs 98 are disposed between the panel portions 96 and 97,all of which are constructed from the preferred composite material asdescribed in detail below. A pair of flanges 102 and 104 are disposedalong the longitudinal side edges of the decking panel 95. The flanges102 and 104 are sized and shaped to permit a plurality of such panels 95to be laid next to each other side to side and interconnected at theiradjacent flange portions. In this manner, a plurality of such deckingpanels 95 may be interconnected to create a single large decking areausing the present invention.

[0064] An alternate form of a decking panel 95′ is illustrated in FIG.17. In this form of the invention, the panel 95′ includes an upper panelportion 96′ and a plurality of longitudinal ribs 98′. The longitudinalside edges 106, 108 of this particular embodiment each includes a pairof channels 110, 112 separated by an elongated tongue member 114. Thechannels 110, 112 and the tongue members 114 are designed forinterconnection with other deck panels 95′ utilizing connection rails116. In preferred form, the rail 116 is in the form of a “T” bar havinga top portion 118 for engaging the channels 112 beneath the associatedtongues or lips 114. A base portion or rib 120 depends from the undersurface of the top portion 118 to provide structural stability andstrength for the connection rail 116 between adjacent panels 95′.

[0065] The panel of the invention is designed in such a way that it ispreferably produced on a continuous basis. That is to say, a structuralpanel can be produced in a continuous length with a given web width,preferably 10 ft. wide, using either of the preferred processes outlinedabove. Because the cement that is to be used in the preferred embodimentof the invention is a rapid-setting cement, the material that emergesfrom the downstream end of the belt press is already set. After it hastraveled down the conveyor to the location of the cutting system on themanufacturing line, it is ready to be cut into either panels, wholewalls, floors, or other components, complete with openings for windows,doors, or any other needs. This is one of the key advantages of thepresent invention.

[0066] In one embodiment illustrated in FIG. 4, walls preferably consistof two structural panels facing each other. This is accommodated in theproduction line because the computer system knows that the final wallbeing cut out has certain dimensions of the length and width plusvarious cut-outs for windows, doors and the like. It uses thisinformation to cut off a length of the emerging structural panelsuitable for the entire length of the wall, floor, or whatever is beingmade. It then cuts off an equal length of a further run of thestructural panel. Each of the two panels are then filled with,preferably, a half-inch of aerated fiber fly-ash cement. Foam is thenintroduced to the panels after a suitable drying period, preferablyfifteen minutes or more. All during this time, the cut and part-filledpanels continue to move down the production line.

[0067] When the polyurethane foam, or other type of foam to be used forinsulation, is introduced, the two panels are presented towards eachother with their open cells facing each other as illustrated in FIGS.1-3. The foam fills the entire cavity between the panels, acting to bothinsulate and bond the two panels together. The part-finished panelcontinues to move down the production line, which feeds back on itselfso that it is located back at the cutting station, which in thepreferred embodiment is an automated water-jet cutting system. Theconveyor system must preferably move the material from the belt pressthrough the initial cutting-to-length of the construction panels to theaerated-cement filling station, and then back on itself to the water-jetor other cutting system.

[0068] At this time, openings can be cut in the panels for windows anddoors. If a secondary moisture barrier is required, sheet material madefrom fiber fly-ash cement composite may be fed from another press ontothe finished panel before openings are cut for windows and doors. Thismaterial is fed onto the part-finished honeycomb panel's outer surfacewhile it is still wet and capable of bonding. Mechanical means may beneeded to press both the corrugated drainage cavity 100 (FIG. 2) and theexterior finished surface onto each other and the honeycomb panel.

[0069] In another preferred embodiment of the invention, panels extrudedin sections of the type generally illustrated in FIGS. 12 and 13 mayinclude an insulating foam. This foam may be produced by means of aco-extrusion process where, for example, polyisocyanurate orpolyurethane liquid is fed through holes in the ends of an extrusion dieduring the formation of the hollow sections of the panels. In thismanner, the hollow cavities may be both thermally insulated andstrengthened by the bonding provided by the polyisocyanurate orpolyurethane foam after it expands into the hollow formed sections. Itis necessary to contain the sections thus formed in a press or otherrestraining means to ensure that the expanding foam does not distort theextruded sections. This is particularly true while the extrudedcomposite cement is still setting. Once the extrusion has set, it ismoved to the automated water-jet or other cutting system. At thislocation, the panel may be cut to length or be cut for openings forwindows and doors as in the previously described embodiment.

[0070] In another embodiment of the invention, pillars separate theprimary and secondary moisture barriers. These pillars can be madeeither from polyurethane or other similar foam, fly-ash cement, aeratedfly-ash cement, or other cement. In FIG. 2, a corrugated drainage cavity100 is provided.

[0071] The combination of the continuous production of honeycomb paneland a cutting system such as an automated water-jet cutting system isanother key advantage of the present invention. It means that componentsare produced on a continuous basis and easily cut in an automatedfashion precisely to the needs of the user. It would be quite possiblefor an individual architect to download an individual design to thecutting system in order to have a single unique wall or other componentcut from the emerging assembled material.

[0072] The panel of the invention can be made in a variety of cellsizes, or hollow-section profiles and sizes, depending upon theapplication to which it is to be put. For interior walls, celldimensions can be as little as 20 mm across and 20 mm deep. For a wall,roof or floor, cells of 75 mm or 100 mm may be desirable. For hollowextruded sections, cross-sections may vary from a few mm across tohundreds of mm. For trim to the outside of a house, panels may only be 8mm thick, with interior cell depths as little as 6 mm or less. Suchpanels can be used for siding or other trim pieces to be applied to thebuilding. Other components, such as doors, can be manufactured fromhoneycomb panels that are typically 20 to 30 mm thick, resulting in anoverall door thickness of 40 to 60 mm, for example. For extrudedsections, which is the preferred method, entire doors can be made in asingle drawing operation. These structures can be made in many differentgeometry's, depending upon their purpose. Some components may require agreater fire rating and would therefore have a greater wall thickness orutilize aerated cement placed in the base of each honeycomb cell orextruded section. On the other hand, other components may be optimizedfor lightness, with very thin walls and without an aerated cement layerdeposited in the honeycomb cells or extruded sections.

[0073] The present invention has developed a technology consisting ofpanels made with a thin-wall cellular or tubular structure to producehigh strength and low weight, made from cellulosic or polymer fiber. Theresulting hollow panels are incredibly strong and lightweight. Theactual dimensions of the geometric structure are variable for theintended use. Wall and skin thicknesses as well as section or cell depthand geometry are dependent on the final use of the panel structure.There are several structures capable of filling the design requirementsof the invention. These include cells or sections that form squares,spheroids, triangles, hexagons and other suitable patterns. Preferredwall thickness of the shapes can vary from about 2 mm to 20 mm, withcell depths from about 2 to 100 mm, and extruded cross sections from avery few mm to many hundreds of mm.

[0074] Some products that may be made from the present invention includelightweight construction wall, floor, decking and roof panels andlightweight doors, trim and roof-tile panels. Each of these two genericproduct types is outlined briefly below. Planks come in variousthicknesses, from 8 mm ({fraction (5/16)} inch) up, with finishes suchas wood grain, smooth, etc., depending upon the application. Doors aretypically two inches thick, made from extruded sections or back-to-backhoneycomb panels. Wall and floor panels are similar in concept but aremuch thicker, typically three inches for cellular panels, and can bemade back to back to form six-inch or greater building panels. Forextruded wall sections thickness is typically 3 to 8 inches, andtypically 10 to 14 inches for roof and floor sections. Thicker sheets ingeneral give better thermal insulation, fire-shield, and structuralperformance.

[0075] A small practical plant can manufacture from between 1 and 30million square feet of panel a year, depending on panel thickness andcomplexity. If the present invention's design objective of >50 percentfly ash based raw-material content of the production is achieved,significant quantities of this waste material can be put to productiveuse.

[0076] Referring now more specifically to the fly ash cement compositeof the present invention, it has been shown and is disclosed herein thatthe physical properties of commercially available fly ash cementproducts, which have relatively high lime (CaO) content such as thosemanufactured by Mineral Resource Technologies, LLC, (MRT) and ISGResources (ISG), can be significantly improved in the composition of theinvention by the addition of a dry flue gas desulferized (DFGD) fly ash.Two types of DFGD were used in an experiment based on the sources of thedesulferized fly ash, designated Type F-DFGD and Type C-DFGD. Both typesof DFGD, when combined with either of the above listed commercial flyash cements, produced cement that was both lighter (less dense) andstronger. In some cases, as with a 33wt % Type F-DFGD and 66wt % MRTcement, the improvement in modulus of elasticity (MOE) was over 95%. TheClass F-DFGD fly ash has a relatively low (12%) CaO content and arelatively high carbon content. These two factors should normally makethis ash perform quite poorly as a cementious product. However, when itwas blended with commercially available fly ash cement, the Class F-DFGDfly ash provided exceptional strength increases. The Class C-DFGD flyash mixes resulted in lower strength gains when compared to the ClassF-DFGD fly ash mixes. Traditionally, Class C commercial grade fly asheshave provided a greater cementious benefit to cement mixes. However,when it is mixed with the Class C-DFGD, this does not appear to be thecase. The mechanism for both the strength increase with Class F-DFGD andlower strength gain with Class C-DFGD fly ash is uncertain at thepresent time.

[0077] This experiment example was designed to determine the effect ofdry flue-gas desulferized fly ash (DFGD) upon incorporation intocommercial grade, fly ash based cement. The sample production procedurefor the fly ash cement samples used in this example was standardized andadhered to the manufacturer's specifications. The amount of activationingredient was fixed relative to the amount of cement. For the MRTcement, the activator to cement ratio was 0.018, while the ISG cementrequired 0.lwt % of the total cement mixture weight. The relative amountof DFGD fly ash in the total cement mixture varied by weight amount ofthe total cement mixture.

[0078] The initial step of this example was to blend the weighedproportions of DFGD fly ash and commercial fly ash cement by dry-mixingfor 5 minutes. After the dry mixing, the chemical activators were addedper the manufacturers instructions and allowed to mix for 4 minutes. Thecement slurry was then placed into a mold and tamped into place suchthat each sample cavity was completely filled. The sample mold was thenplaced into a press which consolidated the samples through vibratoryaction for 90 seconds at 6 psi of pressure. The press pressure was thenincreased to 12 psi, and the samples were allowed to cure under pressurein the press. A portion of the cement mixture was then placed on athermocouple and the temperature recorded digitally as the cement set.

[0079] From thermodynamics, it is known that thermal effects accompanyphase transitions. In this example temperature data was used to view thecementitious reaction as it occurred. Once set, the samples were removedand allowed to cure in an ambient atmosphere for seven days. Physicaltesting was then done and the data analyzed. To test the overall effectof a DFGD fly ash included into a commercial fly ash cement mixture, aninitial experiment was run for cement mixtures with DFGD fly ash tocommercial cement ratios of 1:2 and 1:1 respectively. An analysis of thedata showed a change in physical properties.

[0080] Before any DFGD fly ash was added to the commercial cements, theproperties of the commercial cements were determined. MRT's fly ashbased cement gave average MOE values of 4.4 GPa and a density of 2.14g/cm³, while ISG's fly ash based cement gave average MOE values of 6.8GPa with a density of 2.18 g/cm³. These values were set as relativevalues from which to measure any change in physical propertiesassociated with addition of DFGD fly ash.

[0081] The results from the initial DFGD/commercial cement mixturetrials showed a marked increase in strength properties and a decrease indensity. The largest, average MOE value was 9.9 for a cement mixturethat contained 33.3wt % Class F-DFGD fly ash and 66.6wt % ISG cement.This value corresponds to a 95% increase in MOE and was accompanied byan 8% decrease in density. This data set also indicates that lesseramounts of Class F-DFGD have a more drastic effect on the strengthcharacteristics of the cement, i.e. stronger and lighter samples aremade from cement mixtures with less than 50% Class F-DFGD fly ash. Theresults of the MRT cement Class C-DFGD experiments also indicated that alighter, stronger sample can be made with less than 50% Class C-DFGD flyash. Of the two DFGD fly ashes used in this particular example, theClass F-DFGD fly ash was capable of a much larger increase in MOEvalues. When mixed with the MRT cement in a two to one ratio, theincrease in MOE was over 93% from the baseline MRT fly ash cement value.However, it was shown explicitly that incorporation of any DFGD fly ashinto commercial fly ash cement increased the strength (MOE) of theresulting cement mixture and decreased the density. TABLE 1 AverageModulus of Elasticity Values (GPa) Percent DFGD Fly Ash Mix 0% 33% 50%MRT/Class F-DFGD 4.4 8.6 5.3 MRT/Class C-DFGD 4.4 5.8 5.1 ISG/ClassF-DFGD 6.8 9.9 8.0 ISG/Class C-DFGD 6.8 5.7 6.9

[0082] There was a substantial increase in strength associated with theaddition of DFGD fly ash into the ISG cement. The ISG and Class C-DFGDmixtures indicated that stronger cement can be made with larger amountsof Class C-DFGD fly ash. The true optimum ratio may lie between the twodata points. TABLE 2 Average Specific Gravity Values Percent DFGD FlyAsh Mix 0% 33% 50% MRT/Class F-DFGD 2.18 1.94 1.83 MRT/Class C-DFGD 2.181.97 1.92 ISG/Class F-DFGD 2.00 1.90 1.80 ISG/Class C-DFGD 2.02 1.981.92

[0083] The density decreased with increased DFGD fly ash content. Whencompared with MOE values, it is clear that there is a decrease indensity accompanied by an increase in strength.

[0084] The cementitious reaction that occurs with fly ash cement isexothermic and leaves a distinct thermal signature. On a temperatureversus time plot, the initial set time corresponded to the beginning ofthe reaction curve, and the final set time corresponded to the maximumof this curve. By comparing the final set times for cement mixtures withvarious amounts of DFGD fly ash, an understanding of the reactionkinetics for cementization was ascertained. The ISG cements reactedquite vigorously, the steep slope of the time vs. temperature plotillustrating this point. The MRT cement reacted more slowly as was seenin the gradual slope of the time versus temperature plot. Thermal datafrom these experiments showed a reaction delay associated with additionof both types of DFGD fly ashes. For example, the final set time for ISGcement increased from 56 minutes in the raw form to 138 minutes at a 2:1ISG cement to DFGD fly ash ratio. The same trend held true for MRTcements. There does not, however, appear to be any degradation in theoverall intensity or strength of the reaction. The reaction was simplydelayed. The mechanism for this is not known.

THERMAL EXAMPLE I

[0085] Sample Run #150: This represents thermal data for an ISG cementwithout DFGD fly ash. The sharp temperature rise at the set time ischaracteristic of ISG cements, possibly due to lack of retarders. Theinitial set occurred at 34 minutes, while the final set occurred at 55.7minutes. These times are measured from the addition of the activator.

THERMAL EXAMPLE II

[0086] Sample Run #151: This particular experimental example representedthermal data for a 2:1 ISG cement to cement mixture. This illustratedthat the cementitious reaction was no less intense with Class F-DFGD,only delayed. The initial set occurred at 108 minutes while the finalset occurred at 138 minutes after the activator was added to the cementmixture.

THERMAL EXAMPLE III

[0087] Sample Run #152: This showed thermal data for an MRT cement with33% Class F-DFGD fly ash. The gradual temperature rise at set time wascharacteristic of MRT cement, possibly due to the presence of retardersin the mix. Given the gradual slope of this curve, an initial set timewas arbitrary, but the final set time, as indicated by the peaktemperature, was reached 101.7 minutes after the activator was added.

[0088] During sample preparation, it was noted that the DFGD-addedcement mixtures required more water relative to the pure commercialcement to reach the proper consistency. One possible reason for thisphenomenon is the smaller particle size of the DFGD fly ash. A smallerparticle size is analogous to a larger overall surface area and a largersurface area requires more water for wetting to occur. It is speculatedthat this smaller particle size also probably contributed to theincreases in strength in that the small particles were capable offilling the interstitial spaces in the commercial cement. According todocumentation, cements with fewer or smaller interstitial spaces aretypically stronger.

[0089] Notes From Particle Microscopy

[0090] Class F-DFGD

[0091] @80X magnification the scale calibrates to 0.01 mm/division

[0092] Large black particle: 0.05-0.06 mm in diameter

[0093] Black groundmass particles: 0.005-0.03 mm in diameter

[0094] White spherical particle (SiO₂): 0.035 mm in diameter

[0095] MRT Fly Ash Cement

[0096] @80X magnification the scale calibrates to 0.01 mm/division

[0097] Large amorphous white particle (CaO): 0.17 mm across

[0098] White sphere I: 0.04-0.05 mm in diameter

[0099] White sphere II: 0.07-0.08 mm in diameter

[0100] Groundmass particles: 0.005-0.02 mm in diameter

[0101] There is a much larger distribution of particle sizes in thismixture.

[0102] Dry, flue-gas desulferized fly ash, when mixed with commercialfly ash cement, produced a fly ash cement that was stronger and lighterthan commercially available fly ash cements. In one particular mixtureof 33.3% Class F-DFGD and 66.6% ISG cement, the increase in MOE wascalculated at 95% with an 8% reduction in density. The inclusion of adry, flue-gas desulferized fly ash into commercial fly-ash cementproduced an increase in strength with a decrease in density. While it isnot desired to be limited to this explanation, a possible mechanism forthis effect may involve the smaller particle size distributionassociated with DFGD fly ash. When smaller particles are incorporatedinto the commercial fly ash cement matrix, they may fill interstitialspaces and thereby relieve strain on the cement structure, causing fewercracks to develop. A DFGD cement mixture also has a delayed thermalreaction profile, although there is no drastic difference in theintensity of the reaction.

[0103] As can be seen from the above, the present invention seeks toanswer all of these different requirements of a building system in asingle solution. It is a composite material combining the advantages ofall of the systems referred to above. Because it is made from a cement,it should have good fire performance. For the same reason, its water,moisture and rot performance should be superior compared to frame orSIPs. Its resistance to insect attack is also good, because it is acementitious product. It is capable of very high energy efficiency withestimated R-values above 30 for a 6 inch wall. Because it can beconstructed in large panels covering a whole wall or floor, constructiontime is half of other systems, such as frame buildings.

[0104] The present invention is a complete system. In the case of itsbeing made into a wall, this wall requires no further interior orexterior treatment, other than painting. The interior surface is smoothand the joints may simply be taped and painted like drywall. Theexterior surface can be made with a stucco, wood grain, or other surfaceor again may simply be painted. In addition, when design requires it,exterior surfaces, such as siding or other products, may be fixed to thewall if desired. It is believed that the high wind and earthquakeresistance of these composite panels will be exceptionally high due tothe fact that the panel is a composite structure and material.

[0105] Another major benefit of the present invention is that majorcomponents, such as floors, walls and roofs, may be manufactured as acontinuous material. For example, in the case of an exterior wall, thematerial can be made complete, including structure, interior surface andexterior surface. A wall required for the exterior of a house, forinstance, may be cut from material emerging at the end of the productionline, using, for example, a five-axis, water-jet cutting system,computer-controlled and linked via the Internet to a remote CAD stationlocated in an architect's or builder's office. It is believed that thiscapability is unique in the building industry. It will provide theconstruction industry with precision, factory-made, whole walls, floorsand roofs on a very short time cycle, delivered to site for finalerection and finishing. This continuous manufacturing is possiblebecause the material used includes a rapid-setting, fly-ash cement aspart of the composite in the preferred embodiment of this invention.

[0106] The foregoing description and the illustrative embodiments of thepresent invention have been described in detail in varying modificationsand alternate embodiments. It should be understood, however, that theforegoing description of the present invention is exemplary only, andthat the scope of the present invention is to be limited to the claimsas interpreted in view of the prior art. Moreover, the inventionillustratively disclosed herein suitably may be practiced in the absenceof any element which is not specifically disclosed herein.

We claim:
 1. A prefabricated structural panel for use in buildingscomprising: a first sheet having inner and outer planar surfaces; and aplurality of structural ribs disposed on the inner surface of said firstsheet and arranged to form a geometric design having a plurality ofchambers, said first sheet and said structural ribs being integrallyformed as a single unit from a fiber and fly ash composite material. 2.The panel as claimed in claim 1, wherein said panel further comprises asecond sheet formed from said fiber and fly ash composite material andhaving inner and outer planar surfaces, said second sheet inner surfacebeing integrally secured to said structural ribs to close said chambers.3. The panel as claimed in claim 2, wherein said ribs are interconnectedand said geometric design is a honeycomb.
 4. The panel as claimed inclaim 2, wherein said ribs are interconnected and said geometric designis a plurality of rectangular boxes.
 5. The panel as claimed in claim 1,wherein said geometric design is a plurality of substantially parallelchannels, the distal ends of each said channel being open.
 6. The panelas claimed in claim 1, wherein said chambers are filled with insulationmaterial.
 7. The panel as claimed in claim 1, wherein said panel furthercomprises a second sheet formed from said fiber and fly ash compositematerial and having inner and outer planar surfaces, said second sheetinner surface including a second plurality of structural ribs disposedthereon arranged to form a geometric design having a plurality of openchambers facing opposite the chambers of said first sheet structuralribs, said second sheet and said structural ribs being integrally formedas a single unit from a fiber fly ash composite material with said firstsheet.
 8. The panel as claimed in claim 7, wherein said panel furthercomprises an insulation layer interposed between said first and secondsheets and filling the chambers of said geometric structural ribs ofeach said first and second sheets to form an integral prefabricatedpanel.
 9. The panel as claimed in claim 7, wherein said panel furthercomprises a third sheet enclosing the structural rib chambers of saidfirst sheet, and a fourth sheet enclosing the structural rib chambers ofsaid second sheet, and wherein said panel further comprises aninsulation layer interposed between said third and fourth sheets andfilling the space therebetween, said first, second, third and fourthsheets being a single integrally formed extruded panel unit.
 10. Thepanel as claimed in claim 9, wherein said insulation is aerated fiberfly ash.
 11. The panel as claimed in claim 1, wherein said fiber and flyash composite material is a lightweight, quick-setting cementiousmaterial comprising fly-ash cement and organic or inorganic fibers. 12.The panel as claimed in claim 11, wherein said composite materialcomprises 24-99% fly-ash cement, 0-20% fine aggregate and 1-12% fiber.13. The panel as claimed in claim 11, wherein the fiber of saidcomposite material is selected from the group consisting of cellulosicfiber, PVA and polypropylene fiber.
 14. The panel as claimed in claim 1,wherein said composite material comprises a blend of fly ash cement andflue-gas desulfurized fly ash.
 15. The panel as claimed in claim 14,wherein said composite material further comprises said fly ash blendadmixed with fibrous material.
 16. The panel as claimed in claim 15,wherein said fibrous material comprises organic fibers.
 17. The panel asclaimed in claim 14, wherein said blend comprises 30-50% by weight ofsaid flue-gas desulfurized fly ash.
 18. A prefabricated building unitdesigned to form a wall, floor, ceiling or roof of a building, saidbuilding unit comprising: a first panel element including a first sheethaving inner and outer planar surfaces and a first plurality ofstructural ribs disposed on the inner surface thereof with said ribsbeing aligned to form a geometric design having a plurality of openchambers, said first sheet and said first structural ribs beingintegrally formed as a single unit from a fiber fly ash compositematerial; a second panel element including a second sheet having innerand outer planar surfaces and a second plurality of structural ribsdisposed on the inner surface of said second sheet with said second ribsbeing aligned to form a geometric design having a plurality of openchambers, said second sheet and said second structural ribs beingintegrally formed as a single unit from a fiber fly ash compositematerial; and an insulation layer interposed between said first andsecond panels and filling the chambers of said first and secondgeometric structural ribs to form an integral prefabricated buildingunit.
 19. The building unit as claimed in claim 18, wherein said firstpanel element further comprises a third sheet enclosing said firststructural rib chambers of said first sheet, and wherein said secondpanel element further comprises a fourth sheet enclosing the chambers ofsaid second structural ribs, said insulation layer being interposedbetween said third and fourth sheets and filling the space therebetween,said first, second, third and fourth sheets being a single integrallyformed extruded panel unit
 20. The building unit as claimed in claim 19,wherein said the geometric design of said first plurality of structuralribs is different from the geometric design of said second plurality ofstructural ribs.
 21. The building unit as claimed in claim 19, whereinthe chambers of said first plurality of structural ribs remain openwhile the chambers of said second plurality of structural ribs arefilled with said insulation.
 22. The building unit as claimed in claim18, wherein said unit includes web means disposed along opposed sideedges thereof for interconnecting adjacently positioned building units.23. The building unit as claimed in claim 18, wherein said compositematerial comprises a blend of fly ash cement and flue-gas desulfurizedfly ash.
 24. The building unit as claimed in claim 23, wherein saidcomposite material further comprises said fly ash blend admixed withfibrous material of either organic or inorganic origin.
 25. Aprefabricated wall with inner and outer panels separated by insulation,each said panel comprising a sheet having inner and outer planarsurfaces and a plurality of structural ribs disposed on the innersurface thereof with said ribs being arranged to form a geometric designhaving a plurality of open chambers, said sheet and said structural ribsbeing integrally formed as a single extruded unit from a fiber fly ashcomposite material.
 26. The prefabricated wall as claimed in claim 25,wherein each said panel further comprises a second sheet formed fromsaid fiber and fly ash composite material and having inner and outerplanar surfaces, said second sheet inner surface being integrallysecured to said structural ribs to close said chambers.
 27. Theprefabricated wall as claimed in claim 26, wherein said plurality ofchambers disposed in said inner panel are filled with insulation. 28.The prefabricated wall as claimed in claim 27, wherein said insulationcomprises aerated fiber fly ash.
 29. A process for forming aprefabricated structural panel comprising the steps of: forming acomposite material comprising a fiber and fly ash composite; forming anextrusion die, sized and shaped to extrude a panel structure of desiredshape and geometry; extruding said composite material through said diewhere there are a plurality of holes in the mold that allow insulationbonding material to be coextruded and simultaneously deposited into thepanel structure as it is extruded; extruding said composite material andinsulation bonding material through said die onto a first conveyor belt;and compressing said extruded composite with a second conveyor belttraveling substantially parallel with said first conveyor belt torestrain overexpansion of insulation bonding material until saidcomposite structure has set.
 30. The process as claimed in claim 29,wherein said extruded composite panel is unitary and integral.
 31. Theprocess as claimed in claim 29, wherein said fiber and fly ash compositeis formed by admixing fly ash cement with flue-gas desulfurized fly ashto form a blended fly ash cement, and then further admixing fibrousmaterial therewith.
 32. A process for forming a prefabricated structuralpanel comprising the steps of forming a composite material comprising afiber and fly ash composite; extruding or depositing said compositematerial onto the upper surface of a first conveyor belt onto whichinsulating volumes have been placed in a geometric pattern; compressingsaid extruded or deposited composite material while on said firstconveyor belt by pressing said extruded or deposited composite materialwith a second conveyor belt operating substantially parallel with andover the top of said first conveyor belt; and removing said compressedcomposite material from said first conveyor belt onto a third conveyorbelt to enable said compressed composite material to set and harden. 33.The process as claimed in claim 32, wherein the geometric pattern in thesurface of said extruded composite material is formed by placing saidgeometric pattern onto the surface of said second conveyor belt so as toimprint the surface of said extruded composite material as the secondconveyor belt is pressed into said material.
 34. The process as claimedin claim 32, wherein the geometric pattern in the surface of saidextruded composite material is formed by placing a pattern of spheroidsonto the surface of said first conveyor belt prior to extruding saidcomposite material onto said first belt so that the composite materialis applied over said spheroids and fills the voids therebetween to formthe predetermined geometric pattern.
 35. The process as claimed in claim32, wherein said fiber and fly ash composite is formed by admixing flyash cement with flue-gas desulfurized fly ash to form a blended fly ashcement, and then further admixing fibrous material therewith.
 36. Anextrusion process of forming a prefabricated structural panel comprisingthe steps of: forming a composite material comprising a fiber and flyash composite; forming an extrusion die, sized and shaped to extrude apanel structure of desired shape and geometry; extruding said compositematerial through said die alone or in combination with insulationmaterial to be used in conjunction with said composite material; heatingsaid die as said composite material is extruded therethrough toaccelerate the setting of said composite once extruded; and removingsaid extruded composite away from said die with a conveyor mechanism topermit said extruded panel structure to set and harden.
 37. A low cost,lightweight cement composite having a high modulus of elasticity and alow density, said composite cement comprising a mixture of a commercialgrade fly ash having a high lime content and a dry flue-gas desulfurizedfly ash.
 38. A cement composite as claimed in claim 37, wherein saidcommercial grade fly ash comprises a lime content of greater thanapproximately 20 wt. %.
 39. A cement composite as claimed in claim 38,wherein said flue-gas desulfurized fly ash comprises approximately 30-50wt. % of said fly ash mixture.
 40. A cement composite as claimed inclaim 37, wherein said cement composite further comprises fibrousmaterial.
 41. A cement composite as claimed in claim 40, wherein saidcomposite comprises 24-99% fly-ash mixture, 0-20% fine aggregate and1-12% fiber.
 42. A cement composite as claimed in claim 41, wherein saidflue-gas desulfurized fly ash comprises approximately 30-50 wt. % ofsaid fly ash mixture.
 43. A low cost light-weight cement compositehaving a high modulus of elasticity and a low density, said compositecement comprising a mixture of a commercial grade fly ash having a highlime content and a dry flue-gas desulfurized fly ash, and an organic orinorganic fibrous material.
 44. A cement composite as claimed in claim43, wherein said composite comprises 24-99% fly-ash mixture, 0-20% fineaggregate and 1-12% fiber.
 45. A cement composite as claimed in claim44, wherein said flue-gas desulfurized fly ash comprises approximately30-50 wt. % of said fly ash mixture.